Process and apparatus for dyeing wool and other textile fibres



Feb. 10, 1970 a, w. WILSON PROCESS AND APPARATUS FOR DYEING WOOL ANDFiled 00%. 7, 1965 OTHER TEXTILE FIBRES 2 Sheets-Sheet 1 INVENTOR BRUCEWARD WILSON ATTORNEYS -2 Sheets-Sheet 2 INVENTOR 'EJRUCEWARDWILSON B. W.WILSON PROCESS AND APPARATUS FOR DYEING wooL AND OTHER TEXTILE FIBRESATTGRNEYS Feb. 10, 1970 Filed Oct. 7. 1965 United States Patent-O3,494,718 PROCESS AND APPARATUS FOR DYEING WOOL AND OTHER TEXTILE FIBRESBruce W. Wilson, Brighton, Victoria, Australia, assignor to CommonwealthScientific and Industrial Research Organization, East Melbourne,Victoria, Australia, a body corporate Fiied Oct. 7, 1965, Ser. No.493,626 Claims priority, application Australia, Oct. 9, 1964, 50,311/64Int. Cl. D06p 3/14 US. Cl. 854 7 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to an improved process for the dyeing of wool andother textile fibres, and to apparatus for carrying out such a process.More particularly this invention is concerned with a process for thecontinuous.

dyeing of wool or other textile fibres, employing a dyebath in which thedye is dissolved in formic acid.

The basic prinicples involved in the use of formic acid as a dye solventfor W001 dyeing are described in Australian Patent No. 238,540 whichdemonstrates that wool may be very satisfactorily dyed by immersing thewool for a short period in a solution of a dyestuff in formic acidcontaining up to 30% of water, followed by washing with formic acid .(ora solution thereof) and then with water.

The uptake of dye by wool from a formic acid dye bath is very rapid andis complete in a matter of minutes, at the most. Furthermore, the actionof formic acid on wool brings about marked changes in its physicalproperties; the wool loses all of its natural springiness, a certainamount of swelling takes place and a body of wool so treated becomessomewhat jelly-like in its form and behaviour. Thus the dyeing of woolon a large scale by the use of formic acid dye solutions presents anumber of problems in relation to the handling and subsequent treatmentof the wool which necessitated the development of the special techniquesand apparatus which form a part of this invention.=

In overcoming these problems, it is also possible to actually gain someadvantage from their existence and introduce new and useful techniquesnot previously known to the dyeing art-Other fibres, such as silk, whichbehave in a similar manner in formic acid can also be dyed usin Iconcerned with a process "ice press some of the liquor from the fibresto adjust the liquor to fibre ratio to between 2:1 and 6: 1, feeding theimpregnated fibres to a conveyor, allowing the fibres to remain on theconveyor for a period sufiicient to allow the desired dye uptake tooccur, expressing spent dye liquor from the fibres, and washing anddrying the dyed fibres.

For wool dyeing, the preferred concentration of the formic acid isbetween 70% and 80% by Weight and the dyeing is carried out at atemperature between 40 and 80 C.

Preferably, the fibres are washed in a series of formic acid baths ofdeer ing acid concentration and finally in water or dilute alkali.Formic acid baths of 15%, 5% and 1.5% concentrations are particularlysuitable.

More particularly, the invention provides a continuous process for thedyeing of wool, comprising the steps of impregnating a continuous sliverof the wool with a dyeing liquor comprising a solution of a dyestutf in70% to 80% formic acid at a temperature between 40 and 80 C., such thatthe liquor to wool ratio is greater than 6: 1, nipping the impregnatedwool sliver to express some of the liquor from the wool to reduce theliquor to wool ratio to between 2:1 and 6:1 by weight, overfeeding theim pregnated fibres t0 a conveyor, allowing the impregnated fibres toremain on the conveyor for a period suflicient to allow the desired dyeuptake to occur, expressing spent liquor from the wool and washing thedyed wool in a series of formic acid baths of decreasing acidconcentration and finally in a neutral or alkaline water bath and dryingthe dyed wool.

Preferablythe dyeing liquor has a formic acid concentration of75-76.'5%, and a temperature between 60 and 80 C. Preferably also theliquor to wool ratio is about 4:1 to 4.521 by weight.

It is further preferred that the wool is first saturated with the dyeingliquor and then the liquor to wool ratio is reduced to the desired rangeby squeezing or wringing the wool to express some of the liquor from thewool.

The invention also includes apparatus for carrying out the above processand thus according to this aspect of the invention there is providedapparatus for the continuous dyeing of wool or other textile fibres witha formic acid dye liquor, comprising a device for impregnating thefibres with the dye liquor, means for conveying a continuous sliver offibres through the impregnating device, means for squeezing theimpregnated fibres emerging from the device to reduce the liquor tofibre ratio to a desired range,v

a conveyor to hold the impergnated fibres for a period sufficient toallow the desired dye uptake to occur, means for squeezing the fibres toremove the spent liquor from the fibres and means for washing the dyedfibres. The device for impregnating .the fibre sliver with dye or washliquors is preferably a spray device but may also take the form of abath or trough through which the sliver passes, or a combination of suchdevices. I

The means for washing the dyed fibers may be any suitable known textilewashing machinery but preferably consists of one or more. stages in eachof which the fibre sliver is first saturated with a wash. liquor byimmersion.

and then squeezed or wrung to express the wash liquor from the fibres.

The first-mentioned means for squeezing the fibres in the dyeingapparatus preferably comprise a pair of pinch rollers, the clearance*bet ween which is adjustable to permit control of the liquor to fibreratio of the impregnated fibre leaving the pinch.

In order that the invention may be more fully understood a-specificpreferred embodiment of an apparatus for dyeing continuous slivers ofcarded or combed wool and the preferred apparatus for washing such dyedwool will now be described, with reference to the accompanying drawingsin which:

FIGURE 1 is a sectioned elevation of the dyeing section of theapparatus;

FIGURE 2 is a detailed cross-section of the spraying device; and

FIGURE 3 is a front elevation of the washing section of the apparatus.

The apparatus is housed in a chamber 1. The wool sliver 2 is fed intothe apparatus by a pair of feed rollers 3 which grip and feed the sliverthrough an opening 4 in the chamber wall to a spraying device 6, whichis shown in detail in FIGURE 2. and comprises an outer casing 7 and aninner sleeve 8, the walls of which are pierced by a number ofperforations 10. The sleeve 8 is sealed to the outer casing 7 by meansof O-rings 9, and has a waisted central section which provides anannular chamber 11 between the casing 7 and the sleeve 8. The chamber 11is supplied with a formic acid dyesolution via the pipe 12 from a supplypump (not shown) which draws the dye solution from a heated storage tank(also not shown). The solution emerges from the perforations 10 in thesleeve 8 as a series of fine jets. On emerging from the spraying device6 the silver passes between a pair of pinch rollers 13a, 13b, theclearance between the pinch rollers being adjustable so that the ratioof dyeing liquor to wool in' the wool leaving the pinch can be adjustedto the desired range, i.e. preferably between 2:1 and 6:1. Excess dyesolution and overspray are collected in a tray 14 situated below thespraying device and the lower pinch roller and returned to the storagetank via the pipe.

16. Because of the high rate of circulation of the dye solution and thelarge volume of the solution carried over by the wool there is notendency for the dyeing fault known as tailing*in this system.

After leaving the upper pinch roller 13a the wet sliver passesunsupported to an idler roller 17, over this roller, and drops on to oneend of a conveyor belt 18. The length and speed of the belt and the feedrate of the sliver are adjusted so that the wool remains on the belt fora period suflicient to allow the desired dye uptake by the wool. Thelength of the belt required is comparatively short as the wet wool is nolonger elastic but is in fact in the form of a limp, almost jelly-likeribbon which readily stacks up concertina-fashion on the belt andoccupies a very much smaller volume than would be taken up by woolwetted with water. For example, with a sliver running on to the belt at1.25 ft./sec., and the belt moving at ft./min., 150 feet of sliver canbe accommodated on a foot belt for a period of 2 minutes. This period isgenerally sufiicient to ensure a 95-100% reaction of the wool with mostcommercial dyestuffs.

The wool sliver is picked up from the other end of the belt 18 by afurther idler roller 19 and passes to a second pair of pinch rollers21a, 21b, which express most of the residual dye solution from thesliver. The sliver then passes from the pinch roller over another idlerroller 22 and out of the dyeing section of the apparatus through anotheropening 25 in the wall of the chamber 1 and thence to the washingsection. A trough 23 beneath the lower second pinch roller receives thespent formic acid dye solution from the second pair of pinch rollers21a, 21b. The floor 24 of the chamber 1 slopes downwardly towards theexit end'of the apparatus so that any extraneous dye liquor which drainsfrom the belt 18 or other parts of the apparatus can be collectedthrough a drain 26 and recovered. The spent solution and drainings whichusually contains a small amount of the dyestutf together with oil anddirt from the wool, are recovered by batch distillation in a glass-linedkettle (not shown).

In the preferred embodiment of the apparatus, the sliver then passesthrough a series of washing stages which are mostly suitably carried outin the apparatus which is illustrated in FIGURE 3.

In this apparatus, which is also enclosed in a chamber 29, the dyed woolsliver 2 emerging from the dyeing apparatus (FIGURE 1) enters thechamber 29 through an opening 30 and passes over an idler roller 31 thenaround the lower roller (32b) of and between a pair of feed rollers 32a,32b. The lower roller (32b) is partially immersed in a trough 33 whichcontains a wash liquor, most suitably a formic acid solution of about15% concentration. The dyed sliver 2 which is thus saturated with thewash liquorfrom the trough 33, then passes through a pair of pinchrollers 34a, 34b, which express the major part of the formic acid washliquor from the sliver, together with any residual dye solutionremaining from the dyeing process. The liquor thus expressed from thewool is collected in a trough 35 situated beneath the lower pinch roller34b, and passes, via the pipe 36, to the formic acid recovery section ofthe dyeing apparatus.

From the pinch rollers 34a, 34b, the sliver passes over an idler roller37, and thence to a further pair of feed rollers 38a, 38b, the sliverpassing first under the lower roller 38b, which is partially immersed ina trough 39, containing a further wash liquor, desirably a formic acidsolution of about 5% concentration. The sliver now saturated with theacid passes over an idler roller 41 to a further pair of pinch rollers42a, 42b, which again express the acid from the sliver. The acid thusexpressed, which now has a concentration of about 15%, is collected in atrough 43 from which it passes by gravity through the pipe 44 to thetrough 33 to be used in the first washing stage.

'From the pinch rollers 42a, 42b, the sliver passes to a further washingstage involving idler roller 45, a further pair of feed rollers 46a,46b, and a trough 47. The wash liquor for this stage is formic acid andof about 1.5% concentration.

-It is desirable at this stage to provide a short holding period for thesaturated sliver to ensure complete removal of any residual dye liquorand this holding is provided by passing the sliver around a series ofidler rollers 48, 49, 51, before passing the sliver to the next pair ofpinch rollers 52a, 52b, whereby the acid is expressed from the wool (ata concentration now of about 5%) collected in the trough '53, and passedthrough the pipe 54 to the trough 39.

The sliver passes from the pinch rollers 52a, 52b, over a further idlerroller 55, to the last washing stage involving feed rollers 56a, 56b andtrough 57, a holding stage involving idler rollers '58, 59, 61, 62, 63,pinch rollers 64a, 64b and trough 65. The trough 57 is fed with hotwater and formic acid at about 1.5 concentration is col- I lected intrough 65 and passed to trough 47. The sliver then passes out of thewashing apparatus through a further opening 66 in the chamber wall to bedried and gilled in the conventional manner.

The chambers 1 and 30 are totally enclosed except for the openings 4 and25, 30 and 66 respectively. The chambers are constructed of or are linedwith an acidresistant material, a suitable material being polypropylene.The various rollers, troughs, pipes and other parts of the apparatuswhich are contacted by the formic acid or its vapours are alsofabricated from or covered with acid-resistant plastics materials,rubber or acid-resistant metals.

Vent pipes 27 and 67 are provided in the roofs of the chambers 1 and 30respectively and are connected to an exhaust system (not shown) so thata slight negative pressure (with respect to atmospheric pressure) ismaintained within the two chambers to remove acid vapours from thechambers and-to minimise any leakage of such vapours to the atmosphereoutside the chambers which by weight of formic acid. This acid isfractionated in a glass distillation column. 1.5 percent acid isobtained from the top of the column leaving residual acid in the boilercontaining 73-74% by weight formic acid. The strong acid is redistilledfrom a glass lined kettle and made up to 75% by the addition ofcommercial 90% acid before being returned to the dyeing cabinet. Lossesfrom the distillation column and acid lost in the wool drier are smalland are made up by the above addition of 90% formic acid. The 1.5% acidfrom the top of the column is utilized in the last acid-washing step.

In a typical production run, 3.38 kg. (7.47 lb.) of type 64 wool topswas dyed to a shading of 3% with the reactive dyestuff Drimarene RedZ-RL, according to the following procedure:

Drimarene Red Z-RL 146 g. (0.66 lb.) was pasted in a small amount ofcold water and then dissolved in hot water to make a solution containing3.56 kg. (7.75 lb.) of water. This solution was mixed with 18.12 kg. (40lb.) of 90% formic acid to make a dyeing solution of the dyestutf in 75w./w. percent formic acid.

The dye solution was pumped to the storage tank located on the dyeingapparatus described above, and the temperature of the solution wasraised to and maintained at 65-70 C. by circulating the dye solutionthrough a glass coiled heat exchanger. All pipe-lines were made ofpolyethylene and the circulating pump was constructed ofpolytetrafiuoroethylene (Teflon).

The dyeing apparatus was loaded with Wool sliver by drawing the sliverthrough the spraying device and the roller system wtih a fibreglasstape. With the apparatus in motion, the preheated dye solution waspumped to the spraying device and the wool was thus saturated with theformic acid dye solution.

After leaving the spraying device the sliver passed through the pinchrollers 13a, 13 which were adjusted to a clearance of 0.060 to 0.064inch.

The sliver then passed to the conveyor belt 18 and remained there fortwo minutes, after which it was then picked up by the idler roller 19and the second set of pinch rollers 21a, 21b, and the excess 75% formicacid solution squeezed out. By this time 98% of the dye had reacted withthe wool sliver and the solution contained very little visible colour.The weight of the wet wool after squeezing was 8.66 kg. (19.11 lb.) andthe weight of acid removed by squeezing 10.48 kg. (23.13 1b.).

The wool was then washed in the apparatus described above and washedsuccessively in this manner with solutions containing 15, and 1.5%formic acid and finally washed with water. The time taken for eachwashing was two minutes and the temperature of the wash solutions was6070 C. The washed wool was dried without further treatment.

The recovered acid (i.e. 73% formic acid) was mixed with a small amountof 90% acid and a 75 solution was thus prepared for use in furtherdyeings.

Wool dyed as described above has a softer feel than wool dyed byconventional methods but is in no way damaged by the formic acidsolutions used under the conditions described above. The percentagenoils on subsequent processing of the dyed wool is approximately thesame as for conventionally dyed wool.

No special types of dye are necessary and most commercially availabledyestuffs can be used. It has been found that the best results areobtained with the reactive dyestuffs, acid milling dyestuffs and acidlevelling dyestuffs. Chrome blacks can be produced by adding the chrometo the dilute washing stages after dyeing (e.g. at the 1.5 acid washingstage). 1:1 premetallised dyestuffs can also be used but 1:2premetallised dyestuffs are not favoured for use in the method of theinvention.

I claim:

1. A continuous process for the dyeing of wool or other textile fibrescomprising the steps of impregnating a continuous sliver of the fibreswith a dyeing liquor at 40-80 C. comprising a solution of a dye-stuif in-80% by weight formic acid, nipping the impregnated fibre sliver toexpress some of the liquor from the fibres to adjust the liquor to fibreratio to between 2:1 and 6: 1, feeding the impregnated fibres to aconveyor, holding the fibres on the conveyor for a period sufiicient toallow the desired dye uptake to occur, expressing only a portion of thespent dye liquor from the fibres, and washing and drying the dyedfibres.

2. A process as claimed in claim 1, wherein the concentration is from to76.5% by weight.

3. A process as claimed in claim 1, wherein the temperature is between60 C. and C.

4. A process as claimed in claim 1, wherein the liquor to fibre ratio isabout 4:1 to 4.5 :1 by weight.

5. A process as claimed in claim 1, wherein the dyed fibres are washedin a series of formic acid baths of decreasing concentration and finallyin water or dilute a1- kali.

6. A process as claimed in claim 5, wherein three formic acid baths areused successively, the concentrations of the baths being about 15%, 5%and 1.5% respectively.

7. A continuous process for the dyeing of wool comprising the steps ofimpregnating a continuous sliver of the wool with a dyeing liquor at4080 C. comprising a solution of a dyestuff in 70-80% by weight formicacid, nipping the impregnated wool to express some of the liqnor fromthe fibres to adjust the liquor to fibre ratio to between 2:1 and 6:1,feeding the impregnated wool to a conveyor, holding the wool on theconveyor for a period suflicient to allow the desired dye uptake tooccur, expressing only a portion of the spent dye liquor from the wool,and washing and drying the dyed wool.

References Cited UNITED STATES PATENTS 2,460,206 1/ 1949 Wentz 68223,314,256 4/1967 Walsh et a1 6822 3,364,705 1/1968 Thornber 68--22 OTHERREFERENCES Lemin, 1 our. Soc. Dye. & Colour., 74, November 1958, pp.746, 747, 754.

NORMAN G. TORCHIN, Primary Examiner I. E. CALLAGHAN, Assistant ExaminerUS. Cl. X.R. 8-22, 55

